Friday is one of the main characters in Daniel Defoe's 1719 novel 'Robinson Crusoe'. The titular character Robinson Crusoe names the man Friday because they first meet on that day. It is from this character that the expression 'Man Friday' came to describe a male personal assistant or servant, especially one who is particularly loyal.

In the book, Robinson Crusoe is shipwrecked and subsequently spends twenty-eight years on a deserted island off the coast of Venezuela. On his twenty-fifth year on the island, he discovers that cannibals from the mainland sail to the island to kill and eat their captives. Crusoe helps one of the non-English speaking captives to escape, and names him Friday. Initially, they are unable to communicate in words, but Crusoe gradually teaches his new companion to speak English. In thanks for his rescue, Friday acts as Crusoe's servant, thus leading to the idiom "Man Friday".

The name 'Robinson Crusoe' has also led to an idiom: 'robinsonade'. The term was coined by German writer Johann Gottfried Schnabel in 1731 to describe a desert island story or a castaway narrative.

The author, Daniel Defoe (born Daniel Foe; c.1660-1731), produced more than three hundred works, including books, pamphlets, and journals. His novels include 'Robinson Crusoe', 'Captain Singleton' (1720), 'Colonel Jack' (1722), and 'Moll Flanders' (1722).

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